Doesn't even supporting regular MP3 require paying licensing fees to Fraunhofer?
Or do you mean that supporting MP3Pro would require paying ADDITIONAL licensing fees to Franhofer?
http://www.mp3licensing.com/royalty/ says:
Royalty Rates -> PC Software Applications
MP3
Decoder - US$ 0.75 per unit
Codec - US$ 2.50- US$ 5.00 per unit
MP3Pro
Decoder - US$ 1.25 per unit
Codec - US$ 5.00 per unit